1. Field of the Invention
The present invention relates to a flat plasma discharge display device using an AC plasma discharge.
2. Description of the Related Art
For example, Japanese Laid-Open Patent Publication No. Hei 7-220641 has disclosed a flat display device utilizing a plasma discharge.
As an example of a conventional flat display device of this kind, for example, FIG. 6 is a schematic perspective view showing a part cut away, and FIG. 7 is a schematic exploded perspective view showing a flat vessel in which first and second substrates 101 and 102 formed of a glass substrate, for example, are opposed to each other with a needed space held therebetween and the surroundings are sealed with airtightness.
A discharge maintaining electrode group 105 is provided on the internal surface of the first substrate 101, in which plural pairs of first and second discharge maintaining electrodes 103 and 104 are formed of transparent conductive layers making a pair, for example, and are arranged in parallel (only one pair is shown in the drawing).
The discharge maintaining electrodes 103 and 104 formed of the transparent conductive layers have high resistivities and so-called bus electrodes 103b and 104b formed of metal layers having high conductivities are bonded along the side edge opposed to the opposed sides of the discharge maintaining electrodes 103 and 104 making each pair.
Partition walls 106 extended in a direction orthogonal to the directions of extension of the discharge maintaining electrodes 103 and 104 are provided with a predetermined space in parallel and an address electrode group 108 is provided with a stripe-shaped address electrode 107 formed between the partition walls 106 on the internal surface of the second substrate 102. In addition, phosphors R, B and B for emitting red, green and blue colors, for example, by excitation with ultraviolet rays generated through a plasma discharge are coated between the partition walls 106.
FIG. 8 is a view showing the planar arrangement relationship among the first and second discharge maintaining electrodes 103 and 104, the address electrode 107 and the partition wall 106.
The driving operation of the flat plasma discharge display device having the above-mentioned structure applies a needed discharge starting voltage between the address electrode 107 and the first discharge maintaining electrode 103 which are selected respectively, thereby accumulating electric charges in a portion intersecting them and starting a discharge through a high-frequency discharge phenomenon. In this state, a needed alternating voltage is applied between the discharge maintaining electrode 103 and the second discharge maintaining electrode 104 making a pair therewith so that a plasma is generated in a discharge space in this portion and electric charges are accumulated at the same time, thereby continuing the discharge, that is, maintaining the discharge. The phosphors R, G and B having respective colors described above which are positioned in the intersecting portion are caused to emit light with ultraviolet rays generated through the discharge.
In this case, a region enclosed with a solid line a in the intersecting portion of the address electrode 107 and the discharge maintaining electrodes 103 and 104 making a pair almost acts as a discharge region and a region shown in a slant line almost acts as a light emitting region for the phosphor, that is, a pixel region 110 as typically illustrated in FIG. 8, for example. With this structure, the centers of the pixel region and the discharge region are almost coincident with each other.
While the flat plasma discharge display device has been put into practical use, the luminance thereof is insufficient. For example, the luminance in the display panel of the flat plasma discharge display device of this type having a 42 inch screen is approximately 500 cd/m2.
In a finally completed display device using this panel, a sheet or a film for electromagnetic wave shielding and the prevention of external light reflection is overlapped with the display panel. Therefore, the brightness actually observed is reduced very much.
For example, in a so-called reflection type flat plasma discharge display device in which an image is observed on the first substrate 101 side provided with the first and second discharge maintaining electrodes 103 and 104 opposite to the second substrate 102 side provided with the phosphor and the address electrode 107 described above, the light emitting display is observed through the discharge maintaining electrodes 103 and 104. Therefore, it is necessary to constitute them by transparent electrodes. Moreover, even if they are constituted by the transparent electrodes, bus electrodes 103b and 104b are provided thereof so that light shielding is increased in a light emitting portion. Furthermore, even if the discharge maintaining electrodes are constituted by the transparent electrodes, light absorption caused during passage through the transparent electrodes cannot be ignored.
As shown in FIG. 8, furthermore, the centers of the discharge region 109 and the pixel region 110 are almost coincident with each other. Therefore, when a shielding layer for shielding the external emission of unnecessary electromagnetic waves and ultraviolet rays generated in the discharge region 109 is provided, original light emission for display also is reduced.
The above-mentioned matter causes a luminance in the completed flat plasma discharge display device to be reduced.
The present invention provides a flat plasma discharge display device capable of effectively avoiding such drawbacks to obtain bright display.
In the flat plasma discharge display device according to the present invention, a first substrate and a second substrate are provided opposite to each other, a peripheral portion thereof is sealed with airtightness through a frit seal, for example, and a flat airtight space is formed between the first and second substrates.